Klein’s arrangements of lines and conics

Quasi-Configurations Derived by Special Arrangements of Lines

“…The Klein arrangement of lines naturally arises from the subgroup PSL (2,7), the finite simple group of order 168, which is the automorphism group of the Klein quartic curve x 3 y + y 3 z + z 3 y = 0 of P 2 , see [7,8]. It contains 21 involutions, each leaving a line fixed.…”